On converting Node to Sub-graph second time causes to editor freeze, refer the attached video

Steps to repro:
1. Create a new project
2. Window > Package Manager > Shader Graph > Install
3. Project window > Create > Shader > Unlit Graph
4. Open "New Shader Graph" from Project Window
5. Crate any node(Crate Node > Channel > Flip)
6. Select "Flip" Node > right-click > Convert to Sub-graph > Save
7. Repeat step 6 and REPLACE already converted Sub-graph

Actual Result:
Editor freezes on converting Node to Sub-graph twice

Expected Result:
Node gets converted and replaces the existing Sub-graph node gracefully

Reproducible in:
2019.3.0b7, 2019.3.0b8, 2019.3.0a1

Working fine in:
2019.2.6f1

Package version found: 7.1.2, 7.1.1, 7.0.0

Package version working fine: 6.9.2, 6.5.3

Environment:
Windows 10 & macOS 10.14